The present invention relates to a VTOL aircraft, (vertical take-off and landing aircraft) having a thrust/lift/control system integrated into a plurality of controllable pitch propellers mounted in ducts angled downwardly at an acute angle with respect to the longitudinal axis of the aircraft with vertically pivotable deflector vanes in the duct exits and interconnections between the aircraft altitude and attitude controls and the collective blade pitch actuators of selected propellers.
Many types of VTOL aircraft have been proposed and constructed, the most common of which is the conventional helicopter having one or more lifting rotors, of which the blade pitch is controlled both collectively and cyclically for controlling the attitude and altitude of the aircraft. The physical dimensions of even the smaller-sized helicopters, such as a two-man capacity, are relatively large due to the size of the relatively low RPM rotor blades and blade clearance considerations. A high degree of maintenance is required for conventional helicopters primarily due to the relatively complex nature of the rotor assembly in which each blade must be controllable in pitch cyclically during each revolution as well as collectively during an entire revolution and the resultant vibratory forces that are imposed on the rotor assembly.
A small, compact and readily controllable VTOL aircraft, capable of carrying one or two men, would be highly advantageous in many situations, particularly in military operations. A small, compact VTOL aircraft with a low silhouette would provide increased tactical mobility to infantry forces in gaining access to places that are normally inaccessable to motor vehicles due to water and other terrain problems and are inaccessable to helicopters due to terrain clearance problems and obstructions. Even if the rotor blades of conventional helicopters can be aligned in transporting the helicopter, the length of the blades poses dimension problems when transporting the helicopter in vehicles or other aircraft.
Many of the disadvantages of helicopters can be overcome and compactness achieved by substituting one or more vertically aligned shrouded propellers, or ducted fans, for the slower rotating helicopter rotor blades in obtaining the necessary vertical lift required for a VTOL aircraft. Typical of such a vehicle lift required for a VTOL aircraft. Typical of such a vehicle is the flying platform disclosed in U.S. Pat. 3,184,183. However, a flying platform of the nature disclosed in this U.S. Patent must be pitched forwardly at a substantial angle to establish the forward thrust component necessary for forward flight, which causes a marked drag rise, limits the forward flight speed and also creates problems for the occupants. Although the size indicated for the flying platform of the aforesaid patent is moderately compact, 10 feet 10 inches wide and 24 feet 6 inches long, a considerably more compact size would be highly desirable in a two-man VTOL aircraft. Further, the necessity to control the pitch of the rotor blades of the flying platform both cyclically and collectively requires a moderately complex pitch control mechanism with the attendant maintenance problems common to helicopters.
Ducted propeller or fan arrangements of various configurations have been proposed for VTOL aircraft in taking advantage of the well-known greater static thrust that is available from a given amount of power in a shrouded propeller, or ducted fan, arrangement than in an unshrouded propeller of equal size. Configurations of the ducted fans have been proposed in which the axes of the ducts vary from being parallel to the longitudinal axis of the aircraft to being perpendicular to the longitudinal axis and intermediate angles. In these aircraft the exit area of the ducts have vertically pivotable deflector vanes that can be positioned to direct the air flow from the duct in the direction necessary to obtain the desired components of the vertical and forward thrust to support the aircraft in the desired mode of operation, e.g. hovering, vertical ascent or descent or forward motion. Typical of such arrangements are the configurations shown in U.S. Pat. No. 2,932,468 or 3,486,577. In wingless aircraft of the VTOL type utilizing ducted fans for the necessary lift forces, control forces necessary to establish the necessary attitude and direction of movement of the aircraft have been achieved in a variety of ways. Most commonly used were pivotable, elongated vanes arranged longitudinally and transversely of the aircraft axis in the slipstream of the ducted fan in achieving attitude control. However, establishing adequate attitude control forces in the wingless ducted fan type of VTOL aircraft that will function effectively and efficiently in all modes of flight has posed a problem.
An object of this invention is to provide a readily controllable small, compact VTOL aircraft of maximum efficiency.
A further object of this invention is to provide a compact VTOL aircraft of minimum size and low silhouette able to carry one or two men over natural or man-made obstacles.
Yet another object of the invention is to provide a small, compact VTOL aircraft capable of relatively high forward speed.
A further object of the invention is to provide a compact, small VTOL aircraft which is simple in design and requires a minimum of maintenance attention.
Yet still a further object of the invention is to provide a small and compact VTOL aircraft of the ducted fan type which is highly maneuverable and controllable in all modes of operation.